Wartsila 31 Product Manual page 102

9. Cooling Water System
T
Design data:
Fresh water flow
Heat to be dissipated
Pressure drop on fresh water side
Sea-water flow
Pressure drop on sea-water side, norm.
Fresh water temperature after cooler
Margin (heat rate, fouling)
9.3.7 Waste heat recovery
The waste heat in the HT cooling water can be used for fresh water production, central heating,
tank heating etc. The system should in such case be provided with a temperature control
valve to avoid unnecessary cooling, as shown in the example diagrams. With this arrangement
the HT water flow through the heat recovery can be increased.
The heat available from HT cooling water is affected by ambient conditions. It should also be
taken into account that the recoverable heat is reduced by circulation to the expansion tank,
radiation from piping and leakages in temperature control valves.
9.3.8 Expansion tank (4T05)
The expansion tank compensates for thermal expansion of the coolant, serves for venting of
the circuits and provides a sufficient static pressure for the circulating pumps.
Design data:
Volume
Concerning the water volume in the engine, see chapter Technical data.
The expansion tank should be equipped with an inspection hatch, a level gauge, a low level
alarm and necessary means for dosing of cooling water additives.
The vent pipes should enter the tank below the water level. The vent pipes must be drawn
separately to the tank (see air venting) and the pipes should be provided with labels at the
expansion tank.
The balance pipe down from the expansion tank must be dimensioned for a flow velocity not
exceeding 1.0...1.5 m/s in order to ensure the required pressure at the pump inlet with engines
running. The flow through the pipe depends on the number of vent pipes to the tank and the
size of the orifices in the vent pipes. The table below can be used for guidance.
9-14
= HT water temperature after engine (91°C)
out
T = HT water temperature after cooler (38°C)
in
The maximum pressure at the engine must not be exceeded in case an electrically
driven pump is installed significantly higher than the engine.
see chapter Technical Data
see chapter Technical Data
max. 60 kPa (0.6 bar)
acc. to cooler manufacturer, normally 1.2 - 1.5 x the fresh
water flow
acc. to pump head, normally 80 - 140 kPa (0.8 - 1.4 bar)
max. 38°C
15%
min. 10% of the total system volume
NOTE
Wärtsilä 31 Product Guide - a1 - 18 October 2016
Wärtsilä 31 Product Guide